Amlodipine and its salts are long lasting calcium channel blockers useful in the treatment of cardiovascular disorders. Racemic amlodipine is currently used as its besylate or maleate salt in the treatment of angina, hypertension and congestive heart failure. Amlodipine has a chiral centre at the 4-position of dihydropyridine ring and exists in two enantiomeric forms R and S, exhibiting different pharmacological profiles. The S-isomer is the more potent calcium channel blocker, while R-isomer has little or no calcium channel blocking activity. The utilization of optically pure (S)-amlodipine for treatment of hypertension and angina has been disclosed in U.S. Pat. No. 6,057,344.
R-(+)-amlodipine has little activity as a calcium channel blocker, but it is not pharmacologically inert, in fact it is a potent inhibitor of smooth muscle cell migration. (U.S. Pat. No. 6,080,761). Hence, the patients having specific therapeutic requirement of (S)-amlodipine need to be provided the pharmaceutical composition containing (S)-amlodipine, which is substantially free of (R)-amlodipine. There is presently no amlodipine product that contains S-(−)-amlodipine substantially free of the R-(+) enantiomer.